Recycling process for cracking oil



7 May28, 1935.

F. H. EDSON RECYCLING PROCESS FOR CRACKING OIL Filed April 29, 1931Patented May 28, 1935 PATENT OFFICE 2,002,530 RECYCLING PROCESS FORCRACKING OIL Frank H. Edson, Westfield, N. J., assignor to Standard OilDevelopment Company, a corporation of Delaware Application April 29,1931, Serial No. 533,607 2 Claims. (01. 196-48) This invention relatesto improvements in the recycling of hydrocarbon oils during the crackingoperation.

The invention will be fully understood from the following descriptiontaken in connection with the accompanying drawing in which the figure isa diagrammatic side elevational view partly in section illustrating anapparatus for carrying out the invention.

Referring particularly to the drawing, a charging stock is conductedthrough a feed line I and pump 2 through a preheating coil 3 located ina fractionating tower 4. The heated oil is delivered into an accumulator5 from which it flows through line 6 to charging pump 1 which forces theoil under elevated pressure through cracking coil 8 and line 9 into asoaking drum it where it is digested at the desired pressure for asufiicient length of time to facilitate cracking of the oil. Thedigested oil is delivered from the soaking drum through a valved line II into a separator I 2 which is maintained under reduced pressure and inwhich the greater portion of the oil is vaporized. The heavierunvaporized products are removed from the separator through line l3 to asuitable place of disposal, not shown.

The vapors leaving separator l2 are conducted through a line M to afractionating tower I5 which is integral with accumulator 5. The heavierfractions in the vapors condensing in the fractionating tower mix withthe fresh charging stock in the accumulator and the lighter uncondensedfractions are conducted through a line IE to fractionating tower 4. Theuncondensed vapors and a condensed lighter fraction are withdrawn fromthe fractionating tower through lines I! and I 8 respectively to asuitable place of disposal not shown. The relatively heavy fractionscondensing in the fractionating tower are conducted from a reservoir H],which forms the lower section of the tower, through a line 20 and pump2| to the inlet line 6 leading into pump 1. Line 20 preferablyterminates in a suitable injector 22 which opens into the intake of thepump preferably as close as possible to the pump. The condensate isdelivered to the injector under suitable pressure to give suflicientvelocity to the column of combined oils in the pump suction so that theoil will closely follow the pump plunger, during its intake stroke,without substantial vaporization. Any condensate in reservoir I9 inexcess of that required in the system may be withdrawn through line 23to a suitable place of disposal, not shown. The temperature at the topof tower [5 may be controlled by the quantity of condensate admittedthrough line 24. If desired a constant pressure regulator (not shown)may be installed to control the discharge of pump 2!.

By way of example only, and without intention to limit the invention,the charging stock to be cracked can be a gas oil which may be heated to700 F., more or less, in the cracking coil and under a pressure of 500pounds per square inch, more or less. The thus treated oil is deliveredinto the separator l2 at a reduced pressure of, for example, pounds persquare inch, more or less, whereby the greater portion of the oil isvaporized and partially fractionated in tower [5. The condensate, stillunder a pressure of 85 pounds per square inch, more or less, isdelivered to the intake side of the pump 1. The condensed fractions inreservoir [9 are also under a pressure of approximately 85 pounds persquare inch, more or less. The pressure of this condensate is built upby pump 2| sufiiciently so that when the condensate is injected into theintake of pump 1 it will flow at surficient velocity and in sufficientamounts to cause the combined oils on the intake side of the pumpplunger to closely follow the plunger upon its suction stroke withoutsubstantial vaporization. The pressure built up by pump 2! upon-thecondensate in line 20 may, for example, be pounds to pounds per squareinch, more or less.

By the procedure described the condensate from reservoir I 9 is recycleddirectly to the cracking coil under pressure sufficiently high tomaintain it in liquid form without first passing through the accumulator5. As a result, revaporization of the condensate from reservoir l9 whichwould normally occur due to the higher temperatures prevailing inaccumulator 5 is prevented as well as the necessity for refractionatingthe resulting vapors. It will be understood that a portion of theunvaporized oil from accumulator 5 can be introduced into line 20leading to the injector nozzle, if desired. The unvaporized oil can beintroduced into line 20 on the inlet side of pump 2|, if desired.

Various changes may be madev within the scope of the appended claims inwhich it is desired to claim all novelty inherent in the invention asbroadly as the prior art permits.

I claim:

1. In a continuous recycling process for cracking hydrocarbon oil, thesteps which comprise cracking the oil at elevated temperature and underelevated pressure, vaporizing a portion of the thus cracked oil underreduced pressure, partially fractionating the vapors to produce a firstcondensate, recycling the condensate through a pump to the crackingstep, condensing fractions of the remaining vapors to produce a secondcondensate and a desired vapor, and recycling the second condensateunder greater pressure than the pressure on the first condensatedirectly to the intake of the pump at a velocity directed in thedirection of said first condensate entering the intake of said firstpump and high enough to cause the combined oils in the intake side ofthe pump to closely follow the pump plunger upon its suction strokewithout substantial vaporization.

2. Apparatus for cracking oil and recycling con densate which comprisesa heating and cracking element connected with a separator, a'line fordischarging unvaporized oil from the separator, a first fractionatingtower in vapor connection with the separator, a line for removing vaporsfrom said first fractionating tower to a second fractionating tower,'afirst reflux line for removing a relatively heavy condensate from thefirst fractionation tower and delivering it to the heating and crackingelement, a first pump in said first reflux line, a second reflux linefor removing a light condensate from the second fractionating tower anddelivering it into an injector in said first reflux line at the intakeof said first pump, said injector directed along the line of flow of theheavy condensate in said first reflux line, and a second pump forcingthe light condensate in said second reflux line into said 1 injector sothat said light condensate issues from the injector at a velocitypressure toward the intake of said first pump greater than the velocitypressure of said heavy condensate and means for passing fresh oil intosaid first fractionating 20 tower.

FRANK H. EDSON.

